This invention relates to a method, apparatus and system for filling through holes made in a printed circuit board or the like with paste-like substance, and a method, apparatus and system for soldering the printed circuit board or the like filled with the paste-like substance. More particularly this invention relates to a method, apparatus and system for filling the through holes with paste-like substance using a roller with adding power for rotating the roller.
Various methods for printing solder paste on a surface mounting land of a printed circuit board have been disclosed up to now.
In the solder paste printing, usually a mask having openings corresponding to predetermined positions of the printed circuit board is used. By sweeping (dragging) a squeegee, solder paste suitable for the openings is supplied to the printed circuit board through a mask.
In a printed circuit board substrate in which the surface mounting parts land and through holes coexist, as well known, according to one prior method, the solder paste is supplied to the surface mounting part land, and after surface mounting parts are loaded thereon, reflowing is carried out. After that, a lead of each lead provided insertion part is inserted into a through hole coated with flux and soldering is carried out using wave solder. This method requires at least two processes, that is, a process for soldering surface mounting parts by reflowing and a process for soldering lead provided insertion parts with wave solder.
According to this method, a number of reflow frequencies is increased in some types of printed circuit boards loaded with parts and therefore thermal shock to the substrate increases, so that the reliability of the substrate drops. Further, floating of chip parts and the necessary steps for masking with tape or the like cause the increase of the number of steps for mounting process.
According to the prior method, it is impossible to complete soldering with a single reflow by supplying solder paste to the surface mounting land and through holes at the same time, of a substrate in which the surface mounting parts and lead provided insertion parts coexist.
Further because solder volume is reduced about half after the solder is melted, solder paste more than twice a volume of a through hole needs to be supplied to the through hole. Further as the aspect ratio (ratio between a through hole diameter and substrate thickness) increases, it is more difficult to fill with solder paste.
Another prior art method is described in Japanese patent laid open number H05-33742. The document discloses a filling device for filling viscous tungsten paste into a through hole formed on a green sheet. The filling device has a roller squeegee and scrapers for scraping the paste. However the roller squeegee must be forced to rotate. Further the filling device can not supply enough of the paste to the through holes.
An object of the present invention is to provide a method, apparatus and system for supplying solder paste sufficiently to through holes of lead provided parts of a printed circuit board or the like.
Another object of the present invention is to provide a method, apparatus and system for supplying solder paste sufficiently to surface mounting part land and lead provided through holes on a circuit board having a large thickness in which surface mounting parts and lead provided insertion parts coexist at a time.
Still another object of the present invention is to provide a method, apparatus and system for soldering parts with a single reflow to a printed circuit board having a large thickness in which the surface mounting parts and lead provided insertion parts coexist.
To achieve the above objects, according to the present invention, there is provided a paste filling method, apparatus and system for supplying paste-like substance to any through holes formed in an article. The invention provides first, setting a printing mask, which has predetermined openings corresponding to the through holes on the article. Then providing the paste-like substance on the printing mask, and dragging a roller, which is forced to rotate independent of dragging motion, along a surface of the printing mask. After that, removing the printing mask from the article.
According to a further embodiment, the rotation of the roller is carried out so that a peripheral velocity of the roller rotation is a different speed with respect to the roller dragging speed. Preferably the rotation of the roller is carried out so that the peripheral velocity of the roller is faster than the roller sweeping speed.
The invention can be used on articles wherein surface mounting part lands are provided on the article in addition to the through holes so that the paste-like substance is supplied to the through holes and the surface mounting part lands.
According to another aspect of the present invention, there is provided a paste filling method, apparatus and system for supplying paste-like substance to through holes and surface mounting part lands provided arbitrarily on an article, including the steps of matching a printing mask having predetermined openings for through holes and surface mounting part lands therewith in the article and sweeping a roller by rotating the roller independent of the sweeping motion and further sweeping a follow-up squeegee so as to supply the paste-like substance to the through holes. A paste receiving plate is disposed corresponding to the through holes and the surface mounting part lands.
According to still another aspect of the present invention, there is provided a soldering method, apparatus and system for soldering parts on a printed circuit board having through holes and surface mounting part lands. The invention provides for first, matching a printing mask having predetermined openings for the through holes and surface mounting part lands with the printed circuit board. Then, sweeping a roller by rotating the roller and further sweeping a follow-up squeegee so as to supply solder paste to the through holes. A paste receiving plate is disposed corresponding to the through holes and the surface mounting part lands. After loading parts on the surface mounting part lands of the printed circuit board and inserting leads of the parts into the through holes, heating and melting solder paste with the printed circuit board and the paste receiving plate as a set, so as to carry out soldering.
According to the present invention, it is possible to supply paste-like substance to high aspect ratio through holes. It is also possible to supply paste-like substance to the surface and through holes of an article in a time.
Further, in mounting parts onto a printed circuit board according to the present invention, soldering can be carried out by supplying solder paste, loading parts and then melting the solder. As a result, in a printed circuit board in which lead provided parts having leads to be inserted into each through hole and surface mounting parts coexist, the number of steps for mounting process can be substantially reduced thereby contributing to improvement of the reliability of the printed circuit board.